Oh, say can you see the field full of spectators with their mouths open, necks craned, thrilled at the sight of colors bursting in air? At what other time do adults say "Oooooooh" and "Whoa!" without caring what they sound like?

We're all kids on the Fourth of July, because fireworks inspire awe. But though they seem magical, they're actually the result of weeks, or even months, of hard work and planning — plus an understanding of physics, chemistry and engineering.

“"The old-timers hate the technology, and love the thrill of lighting the fuse by hand."”

Julie L. Heckman, executive director of he American Pyrotechnics Association

Local history plays a role in modern-day pyrotechnics, too, says Nunzio Santore, Jr., co-owner, with his brother August, of Garden State Fireworks in Morris County's Millington. The company, which August says supplies 60 to 65 percent of the fireworks used in New Jersey displays, has for the last five years presented the show on the National Mall in Washington, D.C.

"A lot of people of Italian descent, like my grandfather, came here and opened fireworks businesses," Nunzio says. "Seven or eight plants manufactured fireworks just in North Bergen."

The family-owned company is one of the last in the state to manufacture shells used in their shows. "We still go by the standards set by my grandfather," he says. "Some of the books are in Italian."

And that's one of the things we love about fireworks displays: They're timeless. So how do they do it? We get some answers.

What makes fireworks different colors?

"When chemicals are heated to a high temperature, they give off light," says Julie L. Heckman, executive director of the American Pyrotechnics Association. "Each chemical, which is in powder form, will produce a different color." The five most common are strontium carbonate (red); copper chloride (blue); calcium chloride (orange); sodium nitrate (yellow); and barium chloride (green). Just as you would with paints, new shades can be made by mixing chemicals — for example, to get purple, mix strontium (red) and copper (blue).

Is it my imagination, or have the colors gotten more vivid in recent years?

"Over the last few decades, manufacturers have gotten more precise with how they blend chemicals together, and we're seeing a softer palate of colors," says Heckman. "We've been moving away from red, white, blue, green, silver and gold."

August Santore agrees. "More chemicals are available to enhance colors," he says. "If you want to illuminate red, you add magnesium, which makes it burn hotter and brighter, and creates a halo."

How do the chemicals get shot into the air?

The powders are dampened and pressed into tablets or gumball shapes and put into wrapped shells that are fireproofed and dried, with a lift charge added; the tighter the wrapping, says Heckman, the louder the explosion. The shells are then housed in mortars and stabilized on racks.

4th of July in Tenafly. The fireworks are ignited by hand.(Photo: Kevin Riley, Freelance)

The explosives can be set off manually, but more commonly — especially for the bigger shows — a computer program controls when they're ignited, either hardwired or wirelessly using "electronic matches."

How big are the shells?

They range from 3 to 10 inches; for every inch, the shell is expected to rise 100 feet in the air (so a 5-inch shell will reach an apex of 500 feet). Some shells have breaks in them to create a series of bursts.

What safety measures do pyrotechnicians take?

"The old-timers hate the technology, and love the thrill of lighting the fuse by hand," says Heckman. OSHA heavily regulates the protective gear they must wear, which includes hard hats, eye and ear protection and cotton clothing that won't emit static charges.

A family comes out to see fireworks in North Jersey.(Photo: Richard Formicola, Copyright Owned by NJMG - Set Fe)

How do they make sure that fallout from the shells doesn't hurt spectators?

The setting — where roads, spectators and public buildings are — determines the size of the shells, and the amount of fallout from them. Fire trucks can wet down fields in advance, especially if there's been a drought, and stand by during shows.

Why are some fireworks louder than others?

It's the flash powder, says John Sagaria, president of the Rochelle Park-based Fireworks Extravaganza, which has put on Ridgewood's Fourth of July fireworks since 2006. "Flash powder is made of sulfur, potassium perchlorate and aluminum powder, and is very sensitive," he says. "When it explodes, it's called a 'salute.'"

How are fireworks timed to music?

It's all computerized. "You have to make a soundtrack and create a program into the system of whatever you want to see in the sky," August Nunzio says. "There could be a cymbal crash and you want a red break; you have to consider the lift time." On the day of the event, he says, the program is plugged into circuits, and everyone gets to be a spectator, including him.

Macy's Fourth of July Firework's Display.(Photo: Courtesy of Bill Tompkins)

Who has the biggest fireworks show for Fourth of July?

That title goes to Macy's in New York, which uses six barges, and fires off roughly 75,000 aerial shells and effects. Medium-sized cities hold shows half that size.

What's on the horizon (literally)?

"For the past two years, companies have been promoting 'ghost shells,'" says Heckman. "They burst, swirl and just disappear. People are also looking for shapes — dice, hearts, farfalla (which is Italian for butterfly). The industry is trying to put letters into the sky, but it's a challenge, because wind is an issue. A shell could break as an 'm' or a 'w.'"